## Re: [Matplotlib-users] contourf problem

 Re: [Matplotlib-users] contourf problem From: Friedrich Romstedt - 2010-03-29 02:05:45 2010/3/29 Alan G Isaac : > Can you explain this: > norm = colors.Normalize(vmin = -1, vmax = 1) The normaliser takes some arbitrary value and returns a value in [0, 1]. Hence the name. The value \in [0, 1] is handed over to the cmap's __call__(), resulting in the color value. And yes, I guess you can use vmin and vmax directly, it's just a matter of taste. As you can pass in also *boundaries* to Colorbar(), this may be an alternative. It will display all red above the max value, though it's harder to tick. When you want the highest value to be really represented by red, not near-to-red. Friedrich 

 [Matplotlib-users] contourf problem From: Alan G Isaac - 2010-03-28 17:16:51 Using contourf in version 0.99.1, I'm seeing an unwanted white strip to the top and right, adjacent to the axes. (In fact, the strip looks just wide enough to underlay the ticks.) Alan Isaac PS Simple example: x = np.linspace(-5, 5, 100) X, Y = np.meshgrid(x, x) Z = np.sin(x*y[:,None]) fig = plt.figure() ax = fig.add_subplot(1,1,1) ax.contourf(Z) 
 Re: [Matplotlib-users] contourf problem From: Ryan May - 2010-03-28 19:04:31 On Sun, Mar 28, 2010 at 11:16 AM, Alan G Isaac wrote: > Using contourf in version 0.99.1, > I'm seeing an unwanted white strip to > the top and right, adjacent to the axes. > (In fact, the strip looks just wide > enough to underlay the ticks.) > > Alan Isaac > > PS Simple example: > > x = np.linspace(-5, 5, 100) > X, Y = np.meshgrid(x, x) > Z = np.sin(x*y[:,None]) > fig = plt.figure() > ax = fig.add_subplot(1,1,1) > ax.contourf(Z) Well, in your simple example you're not even using the X and Y you calculate to give the spatial dimensions of your data, so it's just using indices, which run from 0 to 99. Since the limits are 0 to 100, bam...white space because, indeed, there is no data. If I do the following example, I don't get any whitespace: x = np.linspace(-5, 5, 100) X, Y = np.meshgrid(x, x) Z = np.sin(x*x[:,None]) #Note change from bug in previous ex. fig = plt.figure() ax = fig.add_subplot(1,1,1) ax.contourf(X, Y, Z) ax.set_xlim(-5, 5) ax.set_ylim(-5, 5) plt.draw() Is there something I'm missing? (Running SVN trunk here) Ryan -- Ryan May Graduate Research Assistant School of Meteorology University of Oklahoma 
 Re: [Matplotlib-users] contourf problem From: Alan G Isaac - 2010-03-28 22:36:50 On 3/28/2010 3:04 PM, Ryan May wrote: > it's just using indices, which run from 0 to 99. Since the limits > are 0 to 100, bam...white space because, indeed, there is no data. > OK, it's obvious one you point it out. Sorry for the typo in the example. Now suppose I want a colorbar labelled at -1, 0, 1 but the highest value realized is <1. Can I somehow use ticks=(-1,0,1) anyway, or do I have to tick at the realized limits and then label "falsely". Here's an example, hopefully without typos this time. x = np.linspace(-5, 5, 101) y = x Z = np.sin(x*y[:,None]).clip(-1,1-1E-6) fig = plt.figure() ax = fig.add_subplot(1,1,1) cax = ax.imshow(Z, interpolation='nearest', extent=[-5,5,-5,5]) cbar = fig.colorbar(cax, ticks=(-1, 0, 1)) As you see, the top tick is not labelled. Thanks, Alan 
 Re: [Matplotlib-users] contourf problem From: Friedrich Romstedt - 2010-03-28 23:20:01 Attachments: norm.py 2010/3/29 Alan G Isaac : > OK, it's obvious one you point it out. > Sorry for the typo in the example. > > Now suppose I want a colorbar labelled at -1, 0, 1 > but the highest value realized is <1. Can I somehow > use ticks=(-1,0,1) anyway, or do I have to tick at > the realized limits and then label "falsely". Here's an > example, hopefully without typos this time. > > x = np.linspace(-5, 5, 101) > y = x > Z = np.sin(x*y[:,None]).clip(-1,1-1E-6) > fig = plt.figure() > ax = fig.add_subplot(1,1,1) > cax = ax.imshow(Z, interpolation='nearest', extent=[-5,5,-5,5]) > cbar = fig.colorbar(cax, ticks=(-1, 0, 1)) > > As you see, the top tick is not labelled. On my machine, it /labels/ the +1.0, so I changed the mismatch to the safe-failing (1 - 0.1) value, in the script attached. Also I fixed your problem, hopefully. Friedrich 
 Re: [Matplotlib-users] contourf problem From: Alan G Isaac - 2010-03-29 01:05:48 On 3/28/2010 7:19 PM, Friedrich Romstedt wrote: > I fixed your problem Can you explain this: norm = colors.Normalize(vmin = -1, vmax = 1) I take it that this scales the range for the color bar, which is what 'luminance' must refer to in the docs? In which case, can we just set vmin and vmax as imshow keywords? patch = ax.imshow(Z, interpolation='nearest', extent=[-5,5,-5,5], vmin = -1, vmax = 1) (Seems to work.) Thanks! Alan 
 Re: [Matplotlib-users] contourf problem From: Friedrich Romstedt - 2010-03-29 02:05:45 2010/3/29 Alan G Isaac : > Can you explain this: > norm = colors.Normalize(vmin = -1, vmax = 1) The normaliser takes some arbitrary value and returns a value in [0, 1]. Hence the name. The value \in [0, 1] is handed over to the cmap's __call__(), resulting in the color value. And yes, I guess you can use vmin and vmax directly, it's just a matter of taste. As you can pass in also *boundaries* to Colorbar(), this may be an alternative. It will display all red above the max value, though it's harder to tick. When you want the highest value to be really represented by red, not near-to-red. Friedrich 
 Re: [Matplotlib-users] contourf problem From: Alan G Isaac - 2010-03-30 16:28:20 > 2010/3/29 Alan G Isaac : > > Can you explain this: > > norm = colors.Normalize(vmin = -1, vmax = 1) On 3/28/2010 10:05 PM, Friedrich Romstedt wrote: > The normaliser takes some arbitrary value and returns a value in [0, > 1]. Hence the name. The value \in [0, 1] is handed over to the > cmap's __call__(), resulting in the color value. And yes, I guess you > can use vmin and vmax directly, it's just a matter of taste. OK, thanks! Alan